This proposal is the beginning of research to extrapolate from cellular electrical properties to gastrointestinal motility in vivo. The frequency of intestinal rhythmicity in vivo is higher than in vitro, possibly due to cholinergic nerves, and acetylcholine (ACh) induces rhythmic activity after ouabain block of slow waves. The nature of the ACh action and its relation to the Na-pump rhythm will be examined. Intestinal segments respond to stretch by either contraction or relaxation according to physiological state and the stimulation appears to be of plexus neurons, not of muscle per se. The neural mechanisms (transmitters) used in local responses will be studied. An animal model for obstructive ileus will be developed. Partial block of intestine leads to hypertrophy proximally, atrophy distally and the hypertrophied region is hyperactive. Properties of the hypertrophied and atrophied muscles will be measured and causes of the structural changes will be sought by means of several surgical procedures.